The two principle figures of merit for a discharge as a source of ultraviolet (UV) radiation are radiant emittance (UV power per unit area at the wall of the discharge tube) and efficiency (UV power output per electric power input). In order to be practicable, a UV discharge source must have a high efficiency and a sufficiently high radiant emittance so that a discharge tube of practical size can produce the desired UV output. Such a UV discharge source which contains mercury is typically applicable to fluorescent lamps. Mercury-based fluorescent lamps provide energy efficient lighting in a broad range of commercial and residential applications. There is increasing concern, however, about the mercury from spent lamps entering the waste stream.
Accordingly, it is desirable to provide a mercury-free discharge source for UV radiation which exhibits high efficiency and high radiant emittance. Furthermore, it is desirable to provide a fluorescent lamp using such a mercury-free discharge source.